My 2001 E150 cargo van ( only 72k mi) has ongoing noises from the differential. It started with a constant droning noise. A good local shop found no damage with the gears, but thought it could be a bearing, so they replaced all the bearings including the axle bearings. A few weeks later, the droning noise is coming back, and a new chirping noise started up, which corresponds with the vehicle speed, best heard around 25 mph. They inspected it again and said the chirping noise was coming from the area of the pinion bearing, so they replaced it again. It didn't change anything.

So my question is what could cause this, if the gears are OK and all the bearings are new, what else could it be?

Signed,
Frustrated!!!

 

Noises in vehicles have a way of telegraphing to different areas making their source sometimes difficult to pin down. It is unfortunate all the extra work was done without correcting the cause.
As far as what else it could be is not the answer. What needs to be done is to isolate/eliminate parts of the driveline or examine all the moving parts like u-joints , center support bearing ,if applicable,transmission and even motor mounts and tires.
To just go off on a wild goose chase and replace parts without being sure, can as you now know, can get to be quite expensive and frustrating. Before allowing any addl work, why not get an additional opinion or two. Good technicians never object to someone else confirming their diagnosis and will even consult with another tech to make sure they are correct. Even if you were to pay for the second opinion it could be cheaper than the pain of replacing good parts.

 

That sounds like good advice. I will talk with another mechanic and get a another opinion on it. Thanks a lot.